1. Field of the Invention
The present invention relates to an optical element, an illumination device, a measurement apparatus, a photomask, an exposure method, and a device manufacturing method.
2. Background
A process of manufacturing a micro device such as a semiconductor device or an electronic device employs an exposure apparatus that exposes a substrate with exposure light emitted from a projection optical system. The exposure apparatus includes a measurement apparatus that measures, for example, optical characteristics of the projection optical system. As the measurement apparatus, for example, as is disclosed in PCT International Publication No. WO2003/029751, a wavefront aberration measurement apparatus, which measures the wavefront aberration of the projection optical system, is known. The wavefront aberration measurement apparatus includes an optical element which has a hole (pinhole) functioning as a quasi point light source. In addition, the apparatus generates spherical waves by irradiating the optical element with irradiation light, and measures a wavefront geometry.